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• Density


  The mass per unit volume of a substance or object
• Calculating density


  1. Mass in kilograms

  2. Volume in meters cubed

  3. Divide mass by volume
• Unit of density


  Kilograms per meter cubed
• The density equation is not given in the exam
• Types of objects


  • Regular objects
  • Irregular objects
• Regular objects


  • Have dimensions that are easy to measure
• Irregular objects


  • Cannot easily measure dimensions
• Determining density of regular objects

  1. Measure mass using balance

  2. Measure dimensions using ruler

  3. Calculate volume from dimensions

  4. Divide mass by volume
• Mass of cube is 0.5 kilograms
• Length of each side of cube is 0.12 meters
• Calculating volume of cube

  Length of side cubed
• Volume of cube is 0.001728 meters cubed
• Density of cube is 289.35 kilograms per meter cubed
• Determining density of irregular objects

  1. Measure mass using balance

  2. Use displacement method to find volume

  3. Divide mass by volume
• Displacement method


  Fill container with water, place object in, measure volume of water displaced
• Volume of displaced water = volume of object
• Density can be calculated from mass and volume
• Plenty of questions on this practical in the revision workbook
• Exothermic reaction


  Reaction that transfers energy from the reacting molecules to the surroundings, causing the temperature of the surroundings to increase
• Endothermic reaction


  Reaction that takes in energy from the surroundings, causing the temperature of the surroundings to decrease
• Energy profile diagram


  1. Shows the energy changes that take place in a reaction

  2. Reactants have more energy than products in exothermic reactions

  3. Products have more energy than reactants in endothermic reactions

  4. Difference in energy between reactants and products is the energy released/absorbed
• Uses of exothermic reactions


  • Hand warmers
  • Self-heating cans
• Activation energy


  Minimum amount of energy particles must have in order to react
• Representing activation energy on energy profile diagram

  Activation energy is the energy from reactants to the peak of the curve